The described invention relates in general to a system for attaching electrical components or electronic components to a substrate and more specifically to a system, device, and method for securing surface-mount devices to molded interconnection devices during affixation by reflow soldering or other methods.
Surface mount technology (SMT) is a known industrial process for constructing electronic circuits in which electrical or electronic components are mounted directly onto a substrate such as a printed circuit board (PCB). Electronic components that are suitable for mounting on such substrates are known as surface-mount devices or “SMDs”. At the positions where SMDs are to be mounted, typical PCBs include flat, electrically conductive pads referred to as solder pads. During the construction process, solder paste is first applied to all the solder pads; then, if components are to be mounted on the second side, a numerically controlled machine places small liquid adhesive dots at the locations of all second-side components. The boards then proceed to pick-and-place machines, where they are placed on a conveyor belt. Small SMDs are usually delivered to the production line on paper or plastic tapes wound on reels. Integrated circuits are typically delivered stacked in static-free plastic tubes or trays. Numerically controlled pick-and-place machines remove the parts from the reels or tubes and place them on the PCB. Second-side components are placed first, and the adhesive dots are quickly cured with application of low heat or ultraviolet radiation. The boards are flipped over and first-side components are placed by additional numerically controlled machines. The use of adhesive dots in this construction process typically requires the surface or substrate to which the various components will be mounted to be held in a horizontal and upright orientation. Additionally, the components are only secure on the surface or substrate to which they are mounted following the low heat or ultraviolet radiation curing process.
The PCBs are then conveyed into a reflow soldering oven. They enter a pre-heat zone where the temperature of the board and all the components is gradually, uniformly raised to minimize thermal stresses when the assemblies cool down after soldering. The boards then enter a zone where the temperature is high enough to melt the solder particles in the solder paste; thereby bonding the component leads to the pads on the circuit board. The surface tension of the molten solder keeps the components in place, and if the solder pad geometries are correctly designed, surface tension automatically aligns the components on their pads. There are a number of techniques for reflowing solder including infrared reflow and various hot gas techniques.
While effective with PCBs, the reflow soldering process is problematic when used with other substrates such as molded interconnection devices (MID). One complication associated with the reflow soldering process occurs when there are multiple, non-parallel or non-horizontal surfaces to which SMDs are to be attached. If the surfaces on an MID to which the SMT components are to be attached are not all horizontally oriented, SMDs may exhibit a tendency to slide off of the MID as the solder paste begins to flow. Movement of the components in this manner is highly undesirable and may result in the assembly of a non-functional or otherwise faulty device. Thus, there is a need for a system and method that will immediately secure SMT components to MIDs or other substrates during reflow soldering or other assembly/affixation processes when the MIDs or other substrates are not horizontally oriented.